1. The Field of the Invention
The present invention relates to methods for manufacturing aryl-aryl coupled polymers using a noble metal catalyst. More particularly, the present invention relates to the manufacture of aryl-aryl coupled polymers and the subsequent separation of the catalyst from the polymer product.
2. The Relevant Technology
The invention relates to the preparation of aryl-aryl coupled polymers. These compounds are of major importance in the high-growth area of conductive or conjugated organic polymers. For example, conductive polymers are important in applications such as polymeric light-emitting diodes, organic solar cells, and organic integrated circuits (ICs).
Currently, conductive polymers have a limited lifetime. Polymer lifetime is possibly the most important issue that determines whether a conductive organic polymer can be used commercially in a particular technology. Recent research shows that the molecular weight and the purity of the polymer are key factors that determine the lifetime of the polymer. In particular, the level of residual noble metal in polymer has a significant effect on lifespan. This is particularly true of blue emitting polymers used in PLED applications.
Conductive polymers can be synthesized by Yamamoto or Suzuki coupling reactions. The Suzuki reaction has been found to be a suitable reaction for the preparation of aryl-aryl coupled conductive polymers. The Suzuki reaction involves the hetero coupling of a halide- or sulphonoxy-functional aromatic compound with a compound containing an aryl-boron functionality in the presence of a base, a palladium compound, and a solvent.
Several variations of the reaction parameters are known. Generally, it is usual to carry out the reaction using two phases: an aqueous phase containing a base and a non-polar organic phase containing the starting compounds and the palladium catalyst. The palladium catalyst is typically a noble metal complexed with a hydrophobic phosphine compound. The solvent used as the non-polar organic phase is typically a solvent such as benzene, toluene, or xylene. The reaction produces a hydrophobic polymer that is soluble in the organic phase.
A significant problem with existing methods of manufacturing conducting polymers using Suzuki coupling is the difficulty in removing the catalyst from the polymer. Since the catalyst is soluble in the same phase as the polymer product, expensive and tedious techniques are required to remove enough metal for the polymers to be used in a commercial application. The difficulty and expense of removing residual noble metal catalysts from polymers manufactured using the Suzuki reaction is a significant impediment to achieving suitable polymer lifetime and economic viability for the use of the polymer in commercial applications.